1. Field of the Disclosure
This specification relates to an electric propulsion system of an electric vehicle, capable of reducing and shielding electromagnetic noise, generated in an electric vehicle using high power, and stabilizing a voltage variation (fluctuation) of DC high-voltage.
2. Background of the Disclosure
Electric vehicles, such as hybrid vehicles or electric propulsion vehicles which are driven by an electric motor, use a high-voltage high-current electric propulsion system (using a DC voltage of 340V to 1000V and a current of 80 A to 300 A). The high-voltage high-current electric propulsion system is configured by including high-power conversion devices, such as an electric generator, a motor, an AC-DC inverter and a DC-DC converter. However, the high power conversion devices are large in size so as to be disposed within a narrow space of the vehicle in a distributing manner.
Specifically, in the aspect that a human and low-voltage electric and electronic devices are present in a high-voltage noise environment formed within a narrow space of the electric vehicle, high-voltage electromagnetic noise may be likely to affect the human body and cause erroneous operations of the electric and electronic devices. While the electric propulsion system is operating, various digital or analog circuits, communication circuits and the like, which use a low voltage below 28V, may be affected by the high-voltage electromagnetic noise. This may cause erroneous operations of various controllers of the vehicle and accordingly bring about an accident of the vehicle. Also, a communication fault (or failure) may be caused in various communication devices mounted in the vehicle, due to electromagnetic noise interference. Actually, a radio, a cellular phone, and other radio devices, whose usage frequency bands overlap a frequency band of the high-voltage noise, may be confronted with degradation of reception sensitivity, and a communication failure of a controller area network (CAN) of a high-voltage battery management system (BMS) may be caused. Consequently, a safety accident may be likely to happen during the travel of the vehicle. Therefore, an electric propulsion system should be designed and fabricated in such a way of preventing the electromagnetic noise or avoid an affection thereby.
An electromagnetic noise generation source in the electric propulsion system is an insulated gate bipolar transistor (IGBT), which is a high-power switching element mounted in an AC-DC inverter, a DC-DC converter and the like. Along a propagation path of high-power switching noise generated from the IGBT may be compositively generated conducted noise due to a leakage current, which is generated from a high-power conversion device, a high-power cable, an electric generator and a motor so as to flow along conductors of a vehicle, and complex radiation noise radiated from a high-voltage power line and the high-power conversion device.
For a 200 kW electric vehicle, more than eight high-power components are interconnected via high-voltage cables. One strand of a high-voltage DC-power cable may be more than 10 mm thick, and the number of power line cables may be totally 16. Also, each power cable may be 1 m to 7 m long. High-voltage 3-phase AC cables of the electric generator and the motor may be more than 10 mm thick and about 5 m long. The AC cables may serve as a propagation path of the electromagnetic noise generated from the IGBT. As the power transfer path extends, the electromagnetic noise may increase and thereby the electric and electronic devices near the power lines may be affected by the electromagnetic waves. Thus, a method of minimizing the electromagnetic noise may be taken into consideration.